The present invention relates to the field of network connections, particularly connections to an electromagnetic network along a drill string used in oil and gas exploration, or along the casing and other equipment used in oil and gas production.
Electromagnetic noise is common on a drilling rig and around a drill string when used in exploration and production of oil and gas, and may interfere with the transmission and reception of electromagnetic signals. An electromagnetic shield, such as a shield in a coaxial cable, commonly used to reduce noise may conduct current between differing potentials on a drill rig and may be a source of electromagnetic noise. Many systems have been developed to compensate for or eliminate the effects of electromagnetic noise.
U.S. Pat. No. 6,232,557 discloses a cable and modular connector system for a power and data transmission network. The cable includes a pair of power conductors and a pair of signal conductors disposed in an insulative cover. The conductors are positioned to minimize differential mode noise imposed on the signal conductors by external sources.
U.S. Pat. No. 6,449,318 discloses a method and system for transmitting data over twisted pair copper wires using a low frequency offset, differential voltage, on-off keying (OOK) transmission technique wherein a floating reference ground set positive or negative for the differential nature of the transmission may be required. The OOK modulated offset low frequency is being keyed to the floating ground reference that is set to a minimum signal to noise ratio (SNR) level. The SNR level may be set by adjusting the voltage separation between floating ground and the offset of the sinusoidal low frequency wave.
U.S. Pat. No. 4,980,682 discloses a borehole telemetry system which has a transmitter located in the borehole, a surface receiver, and surface signal sensors for receiving the transmitted signal. The method places noise sensors where the reception of noise is maximized. Simultaneous measurements are taken of the ambient noise with the noise sensors and the signal sensors. The relationship between the measurements of the noise and signal sensors is determined. The transmitted signal is then received by the signal sensors and simultaneous measurements of the ambient noise are made by the noise sensors. The noise portion of the transmitted signal as received by the signal sensors is determined from the simultaneous noise measurements and the determined relationship. A received signal having reduced noise is then produced by removing the noise portion.